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B-17E Flying Fortress
Design and Development All Variants On 8 August 1934, the U.S. Army Air Corps (USAAC) tendered a proposal for a multi-engined bomber to replace the Martin B-10. The Air Corps was looking for a bomber capable of reinforcing the air forces in Hawaii, Panama, and Alaska.13 Requirements were that it would carry a "useful bombload" at an altitude of 10,000 feet (3 km) for 10 hours with a top speed of at least 200 miles per hour (320 km/h).14 They also desired, but did not require, a range of 2,000 miles (3,200 km) and a speed of 250 miles per hour (400 km/h). The competition for the Air Corps contract would be decided by a "fly-off" between Boeing's design, the Douglas DB-1, and the Martin Model 146 at Wright Field in Dayton, Ohio. The prototype B-17, with the Boeing factory designation of Model 299, was designed by a team of engineers led by E. Gifford Emery and Edward Curtis Wells, and was built at Boeing's own expense.15 It combined features of the experimental Boeing XB-15 bomber with the Boeing 247 transport aircraft.14 The B-17's armament consisted of up to 4,800 pounds (2,200 kg) of bombs on two racks in the bomb bay behind the cockpit, and initially possessed five 0.30 inches (7.62 mm) machine guns. It was powered by four Pratt & Whitney R-1690 "Hornet" radial engines each producing 750 horsepower (600 kW) at 7,000 feet (2,100 m).16 The first flight of the Model 299 was on 28 July 1935 with Boeing chief test-pilot Leslie Tower at the controls.117 Richard Williams, a reporter for the Seattle Times, coined the name "Flying Fortress" when the Model 299 was rolled out bristling with multiple machine gun installations.18 The most unusual gun emplacement was the nose installation (see note for description and drawing), which allowed the single machine gun to be fired toward almost any frontal angle that an approaching enemy fighter would take to attack the B-17.19 Boeing was quick to see the value of the name and had it trademarked for use. Boeing also claimed in some of the early press releases that Model 299 was the first combat aircraft that could continue its mission if one of its four engines failed.20 On 20 August 1935, the prototype flew from Seattle to Wright Field in nine hours and three minutes at an average cruising speed of 252 miles per hour (406 km/h), much faster than the competition.21 At the fly-off, the four-engine Boeing's performance was superior to those of the twin-engine DB-1 and Model 146. Then-Major General Frank Maxwell Andrews of the GHQ Air Force believed that the long-range capabilities of four-engine large aircraft were more effective than shorter-ranged, twin-engined aircraft, and that the B-17 was better suited to their doctrine.22 His opinions were shared by the Air Corps procurement officers, and even before the competition had finished they suggested buying 65 B-17s.2324 Development continued on the Boeing Model 299, and on 30 October 1935, Army Air Corps test-pilot Major Ployer Peter Hill and Boeing employee Les Tower took the Model 299 on a second evaluation flight. The crew forgot to disengage the "gust locks," a system of devices integral to the design that held the bomber's movable control surfaces in place while the aircraft was parked on the ground. After take-off, due to the failure to manually disengage all of the gust locks, the aircraft entered a steep climb, stalled, nosed over, and crashed, killing Hill and Tower (other observers survived with injuries).25261 The crashed Model 299 could not finish the evaluation and, while the Air Corps was still enthusiastic about the aircraft's potential, Army officials were daunted by the much greater expense per aircraft27 (Douglas quoted a unit price of $58,200 based on a production order of 220 aircraft, compared with a price of $99,620 from Boeing28), and as the competition could not be completed Boeing was legally disqualified from the consideration for the contract.24 Army Chief of Staff Malin Craig cancelled the order for 65 YB-17s, and ordered 133 of the twin-engine Douglas B-18 Bolo instead.2324 The loss was not total... but Boeing's hopes for a substantial bomber contract were dashed. —Peter Bowers, 197629 Initial orders Regardless, the USAAC had been impressed by the prototype's performance, and on 17 January 1936, through a legal loophole,30 the Air Corps ordered 13 YB-17s (designated Y1B-17 after November 1936 to denote its special F-1 funding) for service testing.24 The YB-17 incorporated a number of significant changes from the Model 299, including more powerful Wright R-1820-39 Cyclone engines replacing the original Pratt & Whitneys. Although the prototype was company-owned and never received a military serial (the B-17 designation itself did not appear officially until January 1936, nearly three months after the prototype crashed),31 the term "XB-17" was retroactively applied to the airframe and has entered the lexicon to describe the first Flying Fortress. Between 1 March and 4 August 1937, 12 of the 13 Y1B-17s were delivered to the 2nd Bombardment Group at Langley Field in Virginia for operational development and flight tests.32 One suggestion adopted was the use of a pre-flight checklist to avoid accidents such as that which befell the Model 299.30332 In one of their first missions, three B-17s, directed by lead navigator Lieutenant Curtis LeMay, were sent by General Andrews to "intercept" and photograph the Italian ocean liner Rex 610 miles (980 km) off the Atlantic coast.35 The mission was successful and widely publicized.3637 The 13th Y1B-17 was delivered to the Material Division at Wright Field, Ohio, to be used for flight testing.38 A 14th Y1B-17 (37-369), originally constructed for ground testing of the airframe's strength, was upgraded and fitted with exhaust-driven turbochargers. Scheduled to fly in 1937, it encountered problems with the turbochargers, and its first flight was delayed until 29 April 1938.39 The aircraft was delivered to the Army on 31 January 1939.40 Once service testing was complete, the Y1B-17s and Y1B-17A were redesignated B-17 and B-17A respectively to signify the change to operational status.41 Opposition to the Air Corps' ambitions for the acquisition of more B-17s faded, and in late 1937, 10 more aircraft designated B-17B were ordered to equip two bombardment groups, one on each U.S. coast.42 Improved with larger flaps, rudder and a well-framed Plexiglas nose, the B-17Bs were delivered in five small batches between July 1939 and March 1940. In July 1940, a significant order for 512 B-17s was issued;43 however, prior to the attack on Pearl Harbor, fewer than 200 B-17s were in service with the Army.30 A total of 155 B-17s of all variants were delivered between 11 January 1937 and 30 November 1941, but production quickly accelerated, with the B-17 eventually setting the record for achieving the highest production rate for large aircraft.443 The aircraft went on to serve in every World War II combat zone, and by the time production ended in May 1945, 12,731 aircraft had been built by Boeing, Douglas, and Vega (a subsidiary of Lockheed).45464748 Though the crash of the prototype 299 in 1935 had almost wiped out Boeing, now it was seen as a boon. Instead of building models based on experimental engineering, Boeing had been hard at work developing their bomber and now had versions ready for production far better than would have been possible otherwise. One of the most significant weapons of World War II would be ready, but only by a hair. —Jeff Ethell, 198543 Design & Development B-17E The aircraft went through several alterations in each of its design stages and variants. Of the 13 YB-17s ordered for service testing, 12 were used by the 2nd Bomb Group of Langley Field, Virginia, to develop heavy bombing techniques, and the 13th was used for flight testing at the Material Division at Wright Field, Ohio.38 Experiments on this aircraft led to the use of a quartet of turbo-superchargers which would become standard on the B-17 line. A 14th aircraft, the YB-17A, originally destined for ground testing only and upgraded with the turbochargers,57 was re-designated B-17A after testing had finished. As the production line developed, Boeing engineers continued to improve upon the basic design. To enhance performance at slower speeds, the B-17B was altered to include larger rudder and flaps.50 The B-17C changed from three bulged, oval shaped machine gun blisters to two flush, oval-shaped machine gun window openings and a single "bathtub" machine gun housing on the lower fuselage,51 that resembled the similarly configured and located ventral defensive emplacement on the German Heinkel He 111P-series medium bomber. Models A through D of the B-17 were designed defensively, while the large-tailed B-17E was the first model primarily focused on offensive warfare. The B-17E was an extensive revision of the Model 299 design: The fuselage was extended by 10 ft (3.0 m); a much larger rear fuselage, vertical tail fin, rudder, and horizontal stabilizer were added to the design; a gunner's position was added in the new tail; the nose (especially the bombardier's well-framed nose glazing) remained relatively the same as the earlier -B through -D versions had, but with the addition of a Sperry electrically powered manned dorsal gun turret just behind the cockpit, and the similarly powered (also built by Sperry) manned ventral ball turret just aft of the bomb bay – replacing a relatively hard-to-use, Bendix-designed remotely operated ventral turret on the earliest examples of the -E variant, that had also been used on the earlier marks of the North American B-25 Mitchell – resulted in a 20% increase in aircraft weight.57 The B-17's turbocharged Wright R-1820 Cyclone 9 engines were upgraded to increasingly more powerful versions of the same powerplants multiple times throughout its production, and similarly, the number of machine gun emplacement locations were increased to enhance their aircraft's combat effectiveness.58 Operational History The B-17 began operations in World War II with the Royal Air Force (RAF) in 1941 (but was not successful), and in the Southwest Pacific with the U.S. Army. The 19th Bombardment Group had deployed to Clark Field in the Philippines a few weeks before the Japanese attack on Pearl Harbor as the first of a planned heavy bomber buildup in the Pacific. Half of the group's B-17s were wiped out on 8 December 1941 when they were caught on the ground during refueling and rearming for a planned attack on Japanese airfields on Formosa. The small force of B-17s operated against the Japanese invasion force until they were withdrawn to Darwin, in Australia's Northern Territory. In early 1942, the 7th Bombardment Group began arriving in Java with a mixed force of B-17s and LB-30/B-24s.69 After the defeat in Java, the 19th withdrew to Australia where it continued in combat until it was sent back home by Gen. George C. Kenney when he arrived in Australia in mid-1942.70 In July 1942, the first USAAF B-17s were sent to England to join Eighth Air Force. Later that year two groups moved to Algeria to join Twelfth Air Force for operations in North Africa. The B-17s were primarily involved in the daylight precision strategic bombing campaign against German targets ranging from U-boat pens, docks, warehouses and airfields to industrial targets such as aircraft factories.71 In the campaign against German aircraft forces in preparation for the invasion of France, B-17 and B-24 raids were directed against German aircraft production while their presence drew the Luftwaffe fighters into battle with Allied fighters.7 Early models proved to be unsuitable for combat use over Europe and it was the B-17E that was first successfully used by the USAAF. The defense expected from bombers operating in close formation alone did not prove effective and the bombers needed fighter escorts to operate successfully. During World War II, the B-17 equipped 32 overseas combat groups, inventory peaking in August 1944 at 4,574 USAAF aircraft worldwide.72 B-17s dropped 640,036 short tons (580,631 metric tons) of bombs on European targets (compared to 452,508 short tons (410,508 metric tons) dropped by the Liberator and 463,544 short tons (420,520 metric tons) dropped by all other U.S. aircraft).needed The British heavy bombers, the Avro Lancaster and Handley Page Halifax, dropped 608,612 long tons (681,645 short tons) and 224,207 long tons (251,112 short tons) 73 respectively. The Royal Air Force entered World War II with no heavy bomber of its own in service; the biggest available were long-range medium bombers such as the Vickers Wellington which could carry up to 4,500 pounds (2,000 kg) of bombs.74 While the Short Stirling and Handley Page Halifax would become its primary bombers by 1941, in early 1940 the RAF entered into an agreement with the U.S. Army Air Corps to be provided with 20 B-17Cs, which were given the service name Fortress I. Their first operation, against Wilhelmshaven on 8 July 1941 was unsuccessful;7576 on 24 July, the target was Brest, France, but again the bombers missed completely. By September, after the RAF had lost eight B-17Cs in combat or to accidents and many instances of aborts due to mechanical problems, Bomber Command abandoned daylight bombing raids because of the Fortress I's poor performance. The experience showed both the RAF and USAAF that the B-17C was not ready for combat, and that improved defenses, larger bomb loads and more accurate bombing methods were required. However the USAAF continued using the B-17 as a day bomber, despite misgivings by the RAF that attempts at daylight bombing would be ineffective.77 As usage by Bomber Command had been curtailed, the RAF transferred its remaining Fortress I aircraft to Coastal Command for use as a long-range maritime patrol aircraft instead.78 These were later augmented in August 1942 by 19 Fortress Mk II (B-17F) and 45 Fortress Mk IIA (B-17E). A Fortress from No. 206 Squadron RAF sank U-627 on 27 October 1942, the first of 11 U-boat kills credited to RAF Fortress bombers during the war.79 The RAF's No. 223 Squadron, as part of 100 Group, operated a number of Fortresses equipped with an electronic warfare system known as "Airborne Cigar" (ABC). This was operated by German–speaking radio operators who would identify and jam German ground controllers' broadcasts to their nightfighters. They could also pose as ground controllers themselves with the intention of steering nightfighters away from the bomber streams.80 The Air Corps (renamed United States Army Air Forces (USAAF) on 20 June 1941), using the B-17 and other bombers, bombed from high altitudes using the then-secret Norden bombsight, known as the "Blue Ox",8182 which was an optical electro-mechanical gyro-stabilized analog computer.83 The device was able to determine, from variables input by the bombardier, the point at which the aircraft's bombs should be released to hit the target. The bombardier essentially took over flight control of the aircraft during the bomb run, maintaining a level altitude during the final moments before release.84 The USAAF began building up its air forces in Europe using B-17Es soon after entering the war. The first Eighth Air Force units arrived in High Wycombe, England, on 12 May 1942, to form the 97th Bomb Group.85 On 17 August 1942, 12 B-17Es of the 97th, with the lead aircraft piloted by Major Paul Tibbets and carrying Brigadier General Ira Eaker as an observer, were escorted by four squadrons of RAF Spitfires (and a further five squadrons to cover the withdrawal) on the first USAAF heavy bomber raid over Europe, against railroad marshalling yards at Rouen-Sotteville in France, while a further six aircraft flew a diversionary raid along the French coast.8687 The operation was a success, with only minor damage to two aircraft and half the bombs landing in the target area. The raid helped assuage British doubts about the capabilities of American heavy bombers in operations over Europe.88 As the raids of the American bombing campaign grew in numbers and frequency, German interception efforts grew in strength (such as during the attempted bombing of Kiel on 13 June 194389), such that unescorted bombing missions came to be discouraged.90 The two different strategies of the American and British bomber commands were organized at the Casablanca Conference in January 1943. The resulting "Combined Bomber Offensive" would weaken the Wehrmacht, destroy German morale and establish air superiority through Operation Pointblank's destruction of German fighter strength in preparation of a ground offensive.7 The USAAF bombers would attack by day, with British operations – chiefly against industrial cities – by night. Operation Pointblank opened with attacks on targets in Western Europe. General Ira C. Eaker and the Eighth Air Force placed highest priority on attacks on the German aircraft industry, especially fighter assembly plants, engine factories and ball-bearing manufacturers.7 Attacks began in April 1943 on heavily fortified key industrial plants in Bremen and Recklinghausen.91 Since the airfield bombings were not appreciably reducing German fighter strength, additional B-17 groups were formed, and Eaker ordered major missions deeper into Germany against important industrial targets. The 8th Air Force then targeted the ball-bearing factories in Schweinfurt, hoping to cripple the war effort there. The first raid on 17 August 1943 did not result in critical damage to the factories, with the 230 attacking B-17s being intercepted by an estimated 300 Luftwaffe fighters. The Germans shot down 36 aircraft with the loss of 200 men, and coupled with a raid earlier in the day against Regensburg, a total of 60 B-17s were lost that day.92 A second attempt on Schweinfurt on 14 October 1943 would later come to be known as "Black Thursday".93 While the attack was successful at disrupting the entire works, severely curtailing work there for the remainder of the war, it was at an extreme cost.94 Of the 291 attacking Fortresses, 60 were shot down over Germany, five crashed on approach to Britain, and 12 more were scrapped due to damage – a total loss of 77 B-17s.95 A total of 122 bombers were damaged and needed repairs before their next flight. Out of 2,900 men in the crews, about 650 men did not return, although some survived as prisoners of war. Only 33 bombers landed without damage. These losses were a result of concentrated attacks by over 300 German fighters.96 Such high losses of air crews could not be sustained, and the USAAF, recognizing the vulnerability of heavy bombers to interceptors when operating alone, suspended daylight bomber raids deep into Germany until the development of an escort fighter that could protect the bombers all the way from the United Kingdom to Germany and back. At the same time, the German night fighting ability noticeably improved to counter the nighttime strikes, challenging the conventional faith in the cover of darkness.97 The Eighth Air Force alone lost 176 bombers in October 1943,98 and was to suffer similar casualties on 11 January 1944 on missions to Oschersleben, Halberstadt and Brunswick. Lieutenant General James Doolittle, commander of the Eighth, had ordered the second Schweinfurt mission to be cancelled as the weather deteriorated, but the lead units had already entered hostile air space and continued with the mission. Most of the escorts turned back or missed the rendezvous, and as a result 60 B-17s were destroyed.99100 A third raid on Schweinfurt on 24 February 1944 highlighted what came to be known as "Big Week",101 during which the bombing missions were directed against German aircraft production.97 German fighters would have to respond, and the North American P-51 Mustang and Republic P-47 Thunderbolt fighters (equipped with improved drop tanks to extend their range) accompanying the American heavies all the way to and from the targets would engage them.102 The escort fighters reduced the loss rate to below seven percent, with only 247 B-17s lost in 3,500 sorties while taking part in the Big Week raids.103 By September 1944, 27 of the 42 bomb groups of the Eighth Air Force and six of the 21 groups of the Fifteenth Air Force used B-17s. Losses to flak continued to take a high toll of heavy bombers through 1944, but by 27 April 1945 (two days after the last heavy bombing mission in Europe), the rate of aircraft loss was so low that replacement aircraft were no longer arriving and the number of bombers per bomb group was reduced. The Combined Bomber Offensive was effectively complete.104 Notable B-17s Notable B-17sedit All American — B-17F tail# 124406161 survived having her tail almost cut off in a collision over Tunisia, but made it back to base in Algeria — there are false stories about that claim it made it back to Britain. It flew again, but was later scrapped.162163 Aluminum Overcast — flying example. Chief Seattle — sponsored by the city of Seattle, it disappeared (MIA) on 14 Aug 1942164 flying a recon mission for the 19th BG, 435th BS 165 and the crew declared dead on 7 Dec 1945. Hell's Kitchen — B-17F 41-24392 one of only three early B-17F's in 414th BS to complete more than 100 combat missions.166 I'll Be Around — B-17G in the 390th Bomb Group Museum at the Pima Air and Space Museum adjacent to Davis-Monthan AFB near Tucson, AZ. Liberty Belle — former engine testbed restored as flying example, destroyed in a forced landing on 13 June 2011, outside of Chicago, Illinois; no fatalities. Mary Ann — a B-17D that was part of an unarmed flight which left San Francisco on 6 December 1941 en route to Hickam Field in Hawaii, arriving during the attack on Pearl Harbor. The plane and its crew were immediately forced into action on Wake Island and in the Philippines during the outbreak of World War II. It became famous when its exploits were featured in Air Force, one of the first of the patriotic war films released in 1943.167 Memphis Belle — one of the first B-17s to complete a tour of duty of 25 missions in the 8th Air Force, now being restored for display at the National Museum of the U.S. Air Force at Wright-Patterson AFB in Dayton, Ohio. Miss Every Morning Fix'n — B 17C. Previously named 'Pamela'. Stationed in Mackay, Queensland, Australia during World War II. On 14 June 1943, crashed shortly after takeoff from Mackay whilst ferrying U.S. forces personnel back to Port Moresby. 40 of the 41 people on board were killed. It remains the worst air disaster in Australian history. The sole survivor, Foye Roberts, married an Australian and returned to the States. He passed away in Wichita Falls on 4 February 2004. Murder Inc. — A B-17 bombardier wearing the name of the B-17 "Murder Inc." on his jacket was used for propaganda in German newspapers.168 Nine-O-Nine — flying example, Collings Foundation of Stow, Massachusetts. Old 666 — the B-17 flown by the most highly decorated crew in the Pacific Theater Piccadilly Lilly II — 200th from last B-17G to be built, used in the movie Twelve O'Clock High. As of 2011, currently being restored to Flight status, at the Planes of Fame museum. Rosie's Riveters — B-17F bearing serial 42-30758 from the 100th Bomb Group and commanded by highly decorated USAAF officer Robert Rosenthal, it was the lone surviving 100th BG B-17 of the 10 October 1943 raid against Münster to return to the unit's base at Thorpe Abbots. Sally B — The last flying example in Europe. Sentimental Journey — flying example, Commemorative Air Force at Airbase Arizona, Mesa Arizona. Sir Baboon McGoon featured in June 1944 issue of Popular Science magazine and 1945 issue of Flying magazine. Articles talk about mobile recovery crews following Oct 1943 belly landing at Tannington, England. Article omitted return to service in Feb 1944 and seven additional missions. Final crew called it "a real crate" and successfully ditched into North Sea on 29 Mar 1944, a few months before the first article appeared in print. Swamp Ghost B-17E Serial Number 41-2446, a rare surviving "E" model recovered from a Papua New Guinea swamp, now at Pacific Aviation Museum Pearl Harbor. The Swoose — Also nicknamed Ole Betsy while in service, The Swoose is the only remaining intact B-17D, built in 1940, and the oldest surviving Flying Fortress; it is in the collection of the Smithsonian‍ 's Air and Space Museum and is being restored for final display at the National Museum of the U.S. Air Force at Wright-Patterson AFB in Dayton, Ohio, simultaneously with B-17F "Memphis Belle." The Swoose was flown by Frank Kurtz, father of actress Swoosie Kurtz, who named his daughter after the bomber. Texas Raiders — flying example. Last U.S. Navy PB-1W flying, Commemorative Air Force Gulf Coast Wing in Houston, Texas. Yankee Lady — flying example, Yankee Air Force. Ye Olde Pub — the B-17 that Franz Stigler did not shoot down, as memorialized in the painting "A Higher Call" by John D. Shaw.169 5 Grand — 5,000th B-17 made, emblazoned with Boeing employee signatures, served with the 333rd Bomb Squadron, 96th Bomb Group in Europe. Damaged and repaired after gear-up landing, transferred to 388th Bomb Group. Returned from duty following V-E Day, flown for war bonds tour, then stored at Kingman, Arizona. Following an unsuccessful bid for museum preservation, the aircraft was scrapped.170 The So What? I and II — flown by "3 engine Zip" (I was shot down over Germany and II was decommissioned). In game use & Tactics Category:Planes Category:Aircraft Category:American Aircraft Category:Bomber Category:Heavy Bomber